To obtain a variable attenuator having linear characteristics of attenuation vs control current in which the circuit can be matched while exhibiting a constant impedance for variation of attenuation without fail.

PIN diodes 4 and 5 are connected in series between input and output terminals 1 and 2 and a PIN diode 6 is provided between the middle point of a half wavelength line and the ground. The circuit can thereby be matched regardless of the high frequency resistance of the PIN diodes and the relation between a current flowing through the PIN diodes and the attenuation has substantially linear characteristics. Furthermore, transmission loss of a signal transmission path approaches the transmission loss of the half wavelength line at the high frequency characteristics of the PIN diodes are brought higher, and so-called dead loss (insertion loss of the circuit itself not attenuated: transit loss) characteristics are enhanced.